There are a number of well known diagnostic procedures which require a non-surgical entry into the uterus. One such procedure is called hysterosalpingography. Hysterosalpingography is a radiographic method that is used for imaging the anatomical structures of the uterus and fallopian tubes.
Hysterosalpingography generally can be carried out by the introduction of a fine flexible catheter into the cervical canal or uterus, to deliver a contrast medium, such as an iodinated fluid, into the uterus. Radiography is then carried out to provide the imaging information. Another well known diagnostic procedure which entails the non-surgical entry into the uterus is called sonohysterography. This procedure can also employ a fine flexible catheter that is inserted into the cervical canal or uterus. The catheter in this procedure enables the physician or technician to introduce a sterile saline solution into the uterus to expand it so that an ultrasound scanner can be used to sonographically observe the uterus.
In both procedures, the catheter used to introduce the diagnostic fluid into the uterus must also be capable of sealing off the uterus after introducing the fluid to prevent backflow into the vaginal canal. Further, the catheter must also be capable of being anchored in the uterus or cervix to prevent dislodgement of the catheter during the procedure.
Accordingly, prior art catheter assemblies include a catheter having an. inflatable intrauterine balloon made generally from a latex material to seal the uterus and secure the catheter assembly to the uterus to prevent dislodgement during the procedure. One example of such a catheter assembly is shown in FIG. 1A, which shows a catheter 10 having an inflatable intrauterine balloon 14 inserted into the uterus 20. The catheter assembly shown therein is operated by deflating the intrauterine balloon 14 and inserting the distal tip 12 of the catheter 10 through the cervical canal 24 of the cervix 22 and into the uterus 20. The insertion of the distal tip 12 operates to position the deflated intrauterine balloon 14 in the uterus 20. Once positioned, the inflation syringe 16 is used to inflate the intrauterine balloon 14 and the catheter is retracted to place the balloon against the internal os or opening of the uterus. As can be seen in FIG. 1A, once inflated, the intrauterine balloon 14 seals the uterus 20 by blocking the opening leading to the cervical canal 24. A major disadvantage of this design, however, is that the inflated balloon 14 tends to block portions of the uterus during imaging making those portions unviewable.
In order to circumvent this problem, other prior art catheter assemblies as shown in FIG. 1B, have been designed so that the insertion of the distal tip 12 of the catheter 10 into the uterus 20 positions an intracervical balloon 14' in the large spindle-shaped portion 26 of the cervical canal 24. Thus, when the intracervical balloon 14' is inflated, it does not obstruct the uterus 20 during imaging and thereby, allows the entire uterus 20 to be viewed. In practice, however, it has been discovered that when the balloon 14' is inflated in the cervical canal 24, patients experience a considerable amount of pain because the cervix 22 has a large number of nerve endings which makes it very sensitive to the pressure caused by the inflation of the balloon. This problem is made worse by the latex material used in manufacturing these prior art balloons. As is well known in the art, catheter balloons made from latex inflate suddenly in a non-progressive or non-linear manner. The non-progressive inflation rate of balloon catheters made from latex is described in greater detail in U.S. Pat. No. 5,370,618 entitled PULMONARY ARTERY POLYURETHANE BALLOON CATHETER issued to Leonhardt. According to this patent, pulmonary artery balloon catheters made from latex inflate erratically and suddenly due to the relatively high tension of the latex material. This results in a surge to full size when the critical inflation pressure is reached. It is this sudden inflation of the intracervical balloon to full size in the spindle of the cervical canal which intensifies the pain experience by the patient. Moreover, because the inflation rate of the balloon is so sudden, the prior art intracervical balloons have a substantially spherical shape which does not match the ellipsoidal shape of the spindle of the cervical canal.
Further, neither one of the prior art catheters described above can be universally operated so that the balloon can be positioned in either the cervical canal or the uterus whichever is most desirable for a given diagnostic procedure. This necessitates having at least two different types of catheters on hand which is inconvenient and more costly.
It is, therefore, an object of the present invention to provide an improved catheter for non-surgical entry into the cervical canal or uterus, which has an inflatable intracervical/intrauterine balloon that can be inflated progressively in a linear manner to either a substantially elliptical shape or a substantially spherical shape. This provides a catheter that can be operated in either the cervical canal or the uterus.